a. Field of the Invention
The instant invention is directed toward a mechanical seal for controlling delivery of a fluid (e.g., an anticoagulant) for irrigation in basket catheters. In particular, the mechanical seal of the present invention may be used to help direct the fluid between splines of the basket catheter, especially at the apexes, while preventing fluid ingress into the body of the catheter to assist in preventing thrombus formation without inhibiting axial movement of a deployment mechanism for the basket catheter.
b. Background Art
Normal heart rhythm is between 60 and 100 beats per minute. Tachycardia is a fast heart rate (usually over 100 beats per minute) caused by disease or injury. Tachycardias may begin in the upper chambers of the heart (the atria) or the lower chambers of the heart (the ventricles). Some tachycardias are harmless, but other tachycardias are life threatening. Tachycardias can deteriorate to fibrillation, a disorder in which, the heart does not move enough blood to meet the needs of the body.
Atrial fibrillation (AF) is the most common abnormal heart rhythm. It is a very fast, uncontrolled heart rhythm that occurs when the upper chambers of the heart (the atria) try to beat so fast (between 350 and 600 times per minute) that they only quiver. Ventricular fibrillation (VF) occurs when the lower chambers of the heart (the ventricles) produce fast and erratic electrical impulses that fail to induce synchronous mechanical contraction, such that oxygenated blood is not circulated through the body. Fibrillation in the ventricles is a life-threatening arrhythmia demanding immediate treatment.
Before a tachycardia deteriorates to fibrillation, various procedures may be used to treat the heart tissue and reduce or altogether eliminate the occurrence of fibrillations. It is well known that treatment benefits may be gained by creating lesions in the heart tissue, which change the electrical properties of the tissue, if the depth and location can be controlled. For example, cardiac ablation techniques are known for forming lesions at specific locations in cardiac tissue to lessen or eliminate undesirable atrial fibrillations. Likewise, biologic and chemical agents may be delivered into infracted tissue in the lower chambers of the heart (the ventricles) to promote angiogenesis for the treatment of Ventricular Tachycardia (VT). Other procedures are also known for treating these and other ailments. Use of a particular procedure depends at least to some extent on the desired treatment, and may also depend on other considerations, such as tissue characteristics.
A basket catheter may be employed for ablation and other procedures (e.g., mapping) of the heart. The catheter system may include an outer catheter shaft also referred to as a “guiding introducer”. The guiding introducer defines at least one lumen or longitudinal channel. A delivery sheath is fitted through the guiding introducer. To pre-position the sheath at the appropriate location in the heart, a dilator is first fitted through the sheath. In an example of a procedure within the left atrium, the sheath and the dilator are first inserted in the femoral vein in the right leg. The sheath and dilator are then maneuvered up to the inferior vena cava and into the right atrium. In what is typically referred to as a transseptal approach, the dilator is pressed through the interatrial septum between the right and left atria. A dilator needle may be used here to make an opening for the dilator to pass through. The dilator expands the opening sufficiently so that the sheath may then be pressed through the opening to gain access to the left atrium and the pulmonary veins. With the sheath in position, the dilator is removed and the basket catheter, needle, or other device (depending on the procedure) is fed into the lumen of the sheath and pushed along the sheath into the left atrium. When positioned in the left atrium, various mapping and/or ablation procedures, such as the ablation procedures described above, may be performed within the heart.
Several difficulties may be encountered, however, during these procedures using some existing basket catheters. For example, when the basket catheter is expanded within the heart for a procedure, and then collapsed again (e.g., to move to another location within the heart), a slowing or stoppage of the flow blood may occur between the splines of the basket catheter, especially at or near the apexes where the splines are attached to the catheter. This slowing or stoppage of the flow of blood may result in blood clot formation and may possibly lead to a thrombus. A thrombus may decrease blood flow or even completely cut off blood flow, resulting in heart attack or stroke. Indeed, the risk of thrombus formation continues to exist even after the basket catheter has been removed following the procedure.
Thus, there remains a need for preventing thrombus while enabling movement of the catheter shaft during a procedure.